The strategies used during problem-solving are often considered an important indicator of mathematical cognition. These strategies range from observable gestures, like finger counting, to implicit memory strategies like direct retrieval (Geary et al., 1991). Across development, strategy use changes in frequency and type (Siegler, 1987). However, numerous factors can influence both strategy use and accuracy for children and adults alike. The four studies in this international symposium highlight how individual differences in cognitive factors interact with mathematical content, such as variations in problem presentation, as well as how this interaction, in turn, shapes strategy implementation and ultimate math performance.